Some outphasing amplifiers use an isolating combiner to allow signal pre-distortion schemes. However, the isolating combiner includes an isolating load resistor that dissipates a significant amount of power when the outphasing angle is varied to produce low level signals. Multilevel outphasing can be used with the isolating combiner to reduce the amount of wasted energy in the isolating combiner. An outphasing amplifier with a non-isolating combiner (such as a Chireix combiner) is an amplifier circuit that can provide improved power efficiency over a wide input range, e.g., in comparison to an outphasing amplifier with an isolating combiner. The non-isolating combiner is also referred to as a lossless combiner, and the two terms are used herein interchangeably. The power efficiency is a measure of the power needed to operate the amplifier for amplifying an input signal to a specific output level. The improved power efficiency makes such circuit attractive or advantageous for use in some applications. However, the outphasing amplifier with a lossless combiner suffers from low power efficiency in the low input power range, also referred to as the back-off region. There is a need for an improved architecture for the outphasing amplifier with a lossless combiner that overcomes such issue to improve overall power efficiency of the system.